Plasma display devices include a front panel and a back panel, both typically made of inexpensive float or sodalime window glass. Electrical connections and structures are formed on one or both of the panels. For example, the back panel may have a ribbed structure so that the space between these ribs defines a pixel or column of pixels. Plasma displays operate by selectively exciting an array of glow discharges in a confined noble gas mixture, such as He-Xe or Ne-Xe gas mixtures, to produce UV light. Full color displays are made by depositing alternating blue, green and red phosphors in the pixel cells. The phosphors in each pixel cell are excited by the UV light and emit light of the desired color at each pixel position.
The plasma display back panel further has a plurality of parallel, spaced, column electrodes on a surface, with the barrier ribs projecting above and between the column electrodes. The column electrodes required for the display devices are deposited onto a green tape. A plurality of green tapes can also be embossed to form the rib structures on which the phosphors can be deposited to form the pixels. Vias can also be formed in the green tapes by filling them with a conductor ink which provides an electrical connection between the circuits and electronics on the various green tape layers. Drive electronics for the pixels are mounted along the edges of the display. The barrier ribs can also act as spacers between the back panel and a front panel. In a typical display, the barrier ribs are 0.1 to 0.2 mm in height, 0.03 to 0.2 mm wide and have a pitch of 0.1 to 1.0 mm. A support plate underlies the display and provides additional mechanical strength. The support plate can be made of metal, e.g., titanium.
The front panel also includes an array of parallel spaced row electrodes orthogonal to the column electrodes. A layer of glass covers the row electrodes, and a layer of MgO covers the glass layer. A glass frit is used to form a vacuum-tight seal between the front and back panels of the display, confining the noble gases inside the display.
Voltages are selectively applied to the electrodes to excite, maintain and extinguish a plasma in the gas between the barrier ribs. Green tape layers and embedded circuitry are made from materials that, after densification into ceramics, have a thermal coefficient of expansion (hereinafter TCE) that is matched to that of the metal support. The TCE of the ceramic/metal composite matches that of the front panel.
A prior art metal supported plasma display device is illustrated in FIG. 1.
FIG. 1 is a cut-away side plan view taken along a line of a row electrode of the display. The display includes a back panel 10 which includes a metal support sheet 12 and a laminated and embossed green tape stack structure 14 which includes circuitry and which, when embossed, forms the barrier ribs 16 for the display. Embedded in the green tape structure 14 are the column electrodes 20. Above each electrode 20, on the surface of the embossed region of the green tape stack 14, are the alternating phosphors 18 which are excited selectively to emit red, green or blue light. A glass frit seal 24 seals the front glass panel 22 to the back panel 10. Drive electronics 26 drive the display.
In making plasma display devices, it would be desirable to be able to mount the electronic devices needed to address the pixels and to drive the display on the same support board. Unless there is already sufficient space on the sides of the display, in order to do this, a second set of green tape layers would need to be adhered to the backside surface of the metal support board. These green tapes would carry or embed the various interconnects and electronic devices required, solderable pads and the like. In such case, a plurality of feedthrough holes would also need to be made in the support board and filled with a conductive material to permit electrical connections to the circuits and interconnects of the green tapes on both sides of the board. The conductors in the feedthrough holes must be electrically insulated, as with a dielectric material, from the metal plate.
In the past, openings or holes were drilled in the metal support board. A layer of a dielectric was applied to line the openings, and then fired. These dielectric lined openings were then filled with a conductor ink, and fired again. Thus multiple firing steps were employed to form the required conductive feedthrough holes.
It would be desirable to be able to make integrated double sided metal supported display devices using fewer manufacturing steps.